New and improved Israeli reference of birth weight, birth length, and head circumference by gestational age: a hospital-based study.

BACKGROUND: Many centers in Israel still use pre-1970 reference data for neonatal weight, length and head circumference. A recently published population-based reference overestimated the weight of premature infants. OBJECTIVE: To develop a national reference for birth weight, birth length and head circumference by gestational age for singleton infants in Israel. METHODS: Data were collected on all singleton live births documented in the neonatal registry of Rabin Medical Center from 1991 to 2005 (n=82,066). Gestational age estimation was based on the last menstrual period until 1977 and early fetal ultrasound thereafter. Neonates with an implausible birth weight for gestational age (identified by the rule of median +/- 5 standard deviations or expert clinical opinion) were excluded. Reference tables for fetal growth by gestational age were created for males and females separately. RESULTS: The growth references developed differed markedly from the Usher curves currently used in our department. Compared to the recently published population-based birth weight reference, our data were free of the problem of differential misclassification of birth weight for gestational age for the premature infants and very similar for the other gestational age groups. This finding reinforced the validity of our measurements of birth weight, as well as of birth length and head circumference. CONCLUSIONS: Use of our new (birth length and head circumference) and improved (birth weight) gender-specific hospital-based reference for fetal growth may help to define normal and abnormal growth in the neonatal population of Israel and thereby improve neonatal care and public health comparisons.

Are babies getting bigger? Secular trends in fetal growth in Israel--a retrospective hospital-based cohort study.

BACKGROUND: A paradoxical secular trend of an increase in preterm births and a decrease in low birth weights has been reported in many developed countries over the last 25 years. OBJECTIVE: To determine if this trend is true for Israeli neonates, and to add new information on secular trends in crown-heel length and head circumference. METHODS: A hospital-based historic cohort design was used. Anthropometric data for 32,062 infants born at Rabin Medical Center in 1986-1987, 1994-1996, and 2003-2004 were collected from the hospital's computerized registry and compared over time for absolute values and proportional trends. RESULTS: For the whole sample (gestational age 24-44 weeks) there was a significant increase in mean birth weight (by 41 g), crown-heel length (by 1.3 cm), and head circumference (by 0.1 cm) from 1986 to 2004 (P < 0.001). A similar trend was found on separate analysis of the post-term babies. Term infants showed an increase in mean length and head circumference (P < 0.001), but not weight, and moderately preterm infants (33-36 weeks) showed an increase in mean weight (81 g, P < 0.001) and mean length (1.0 cm, P < 0.001), but not head circumference. The proportion of post-term (42-44 weeks), preterm (24-36 weeks), very preterm (29-32 weeks), extremely preterm (24-28 weeks), low birth weight (< 2500 g) and very low birth weight (< 1500 g) infants decreased steadily and significantly over time (P < 0.002). CONCLUSIONS: Babies born in our facility, term and preterm, are getting bigger and taller. This increase is apparently associated with a drop (not a rise) in the proportion of preterm infants. These results might reflect improvements in antenatal care and maternal determinants.